The present invention is directed to a workpiece transfer apparatus for transferring a workpiece to a press. More particularly, the present invention is directed to a shiftable workpiece transfer apparatus for transferring a workpiece to a press while simultaneously shifting the workpiece centerline.
The use of a press to form (draw), trim, bend, pierce or otherwise operate on a sheet metal workpiece is well known. For the sake of simplicity only, all such operations will be referred to herein as “stamping” operations. Such stamping operations are commonly employed, for example, to create vehicle body panels. Depending on the component of interest, and on the specific stamping operation being performed, a single press or a series of presses may be employed.
In either case, a sheet metal blank to be operated upon must be supplied to the press or to each press in a press line for creation of a workpiece of interest. In manufacturing operations, such as vehicle manufacturing operations, these sheet metal blanks are typically supplied in an automated fashion. A number of apparatus may be used for this purpose including, for example, conveyors of various types, walking beam mechanisms, vacuum-based transfer frames and robotic arms. In the case of a single press, the sheet metal blank is supplied to the die, whereafter it is operated upon and then removed from the press to a downstream location. In the case of a press line, the sheet metal blank is supplied to the die in the first press, and then subsequently transferred to one or more following presses in the press line for further manipulation. A press line having multiple presses, each with its own die, is often referred to as a progressive die line. In such a press line, a workpiece is transferred from one press to a subsequent press, such as by one of the transfer mechanisms described above.
In some progressive die operations, a single die may be used to simultaneously operate on more than one sheet metal blank. For example, in a vehicle manufacturing operation, the stamping of a left and right fender or left and right door may be simultaneously performed on a single die. In this case, it is possible and known to use a pair of transfer tables to laterally outwardly shift both workpieces an equal distance during the transfer thereof from one press to a next press. This may be necessary to further separate the workpieces as they are moved from one die to a subsequent and different operation on a next die.
Workspace openings and other physical characteristics of presses and related equipment typically limit the size of a die that may be installed thereto and, therefore, the size of a workpiece that can be stamped. Thus, if it is desired to stamp a larger than typical workpiece, atypical processing steps may be required. For example, in relation to the present invention, an increase in the overall size of a vehicle side panel outer (SPO) workpiece dictates that the centerline of the workpiece be shifted with respect to the centerline of an associated press line as the SPO is moved from one press to a subsequent press. Such shifting is necessary in this case because the increased size of the particular SPO requires an offset of certain die components with respect to the centerline of preceding die (and workpiece). Obviously, the case of a SPO workpiece is used for purposes of illustration only, and the present invention is not limited to use in a process for making any particular workpiece.
The press line on which the SPO of the aforementioned example is manufactured is equipped with a pair of transfer tables, as described above. The exemplary SPO workpiece spans both of these transfer tables and, therefore, both transfer tables are used to transfer the SPO workpiece. While these existing transfer tables are capable of an equidistant lateral shift while moving from one press to the next, they are incapable of cooperating to shift a single workpiece in one lateral direction.
Therefore, it is desirable to be able to shift the centerline of a single workpiece during transfer from one press/die to the next using a pair of workpiece transfer tables that typically may be moved only in a straight line or in opposite lateral directions. Embodiments of the present invention are directed to such a workpiece transfer apparatus and method.